Why car is ticking after warm up?

Sounds like you need a valve adjustment. The sound is the tappets, the part on the rocker arm that makes the valves open and close. If they are worn, they'll make a characteristic tick, tick, tick noise.

If you're a DIY type, here's a youtube vid of the adjustment proceedure on a Honda S2000:

http://www.youtube.com/watch?v=YguimOCYCqY

just be sure to refer to your vehicle's operating manual for the correct settings, as these may vary from your model

Or you can simply add the proceedure to your next tuneup, and should be done every other oil change/tuneup. It's not that much more to have done professionally, and will extend the life of your engine.

Are you low on oil? Have you checked it? Sounds like a valve if you are full of oil, then it may just be time to change it. Oils viscosity wears down after time and will not effectively protect your engine and ticking is one of the first signs the oil is no longer doing its job.

1st i would check the oil, But im sure you have done that, right. So it sounds like the valves have loosened up from just wear and tear, if it has a lot of miles on it, its probably about its time to go, if its going through a lot of oil, then look out.

a sticking hydraulic valve. There is some additive that you can add to the oil that might relieve it. otherwise you got to take the cam off after finding which lifter is sticking..

Use a nice quality oil, it worked for me. I switched over to Mobil 1 and my car is quiet...

You might have worn lifters. Try using Lucas in your oil to see if that helps quiet them down.

Exhaust leak/bad axles.